#include<cstdio>
int n;
long long rez; 
int ciur[100001];
void ReadData(){
    freopen("fractii.in","r",stdin);
    scanf("%d",&n);
    rez = 2 * n - 1;
}

void Ciur(){
    int i,j;
    for(i=2;i<=n;++i)
        for(j=i+1;j<=n;++j)
                if(j%i==0)
                    ciur[j]=1;  
                else
                    rez +=2;
}

void WriteData(){
    freopen("fractii.out","w",stdout);
    printf("%lld\n",rez);
}

int main(){
    ReadData();
    Ciur();
    WriteData();
    return 0;
}